Animated Harmonograph

From Wikipedia:
A harmonograph is a mechanical apparatus that employs pendulums to create a geometric image.
The drawings created typically are Lissajous curves, or related drawings of greater complexity.
The devices, which began to appear in the mid-19th century and peaked in popularity in the 1890s,
cannot be conclusively attributed to a single person, although Hugh Blackburn,
a professor of mathematics at the University of Glasgow, is commonly believed to be the official inventor.